The Mysteries of Atmospheric Electricity

By Rogers D. Rusk M. A.

The Physics of Natures Electricity Simply Explained

The air is in a continual state of
electrification because it contains at
all times small particles charged with
electricity. Even the scientists themselves
do not know just what these
particles consist of because they are different
from the electrified particles found
anywhere else. We are seldom aware of
the existence of these particles because of
their very small size and due to the further
fact that all bodies at or near the surface
of the earth are at practically the same
potential as the earth. However, if all the
electricity in the air could be collected for
use at one time, there would be more, by
far, than we would know what to do with.

Benjamin Franklin startled the scientists
of his day by bringing lightning down on a
kite string, but we can go him one better
today.

ELECTRICITY OUT OF A CLEAR SKY

Even on the clearest day, if we send a
kite up a few thousand feet, a distinct difference
of potential can be noticed between
the ends of the kite wire, often enough to
give a severe shock. The cause of this
electrification has been the subject of much
discussion, but the biggest problem is to
rind just what these minute charged particles
consist of
Ions or small particles charged with electricity
can easily be produced in most any
gas by means of an electrical discharge or
by the influence of X-rays or radium, but
the ions found in the air are different from
these; in fact, they are different from those
found anywhere else, hence it is that they
present a puzzling problem to the scientist.

In general there are three types of ions
which are found in the atmosphere called
the large, small and intermediate. The
small ones which have been known to exist
for a long time are the same as those produced
in any gas by the means above mentioned.
When either an electric discharge.

X-rays or radium rays causes an electron
or element of electricity to be detached
from an atom or molecule to which it belongs,
then it leaves that atom or molecule
charged with the same amount of electricity
of the opposite sign, and the charged particle
is called an ion. Sometimes these particles
group themselves together, thus forming
ions of larger size. Instead of these,
however, there are still larger ions found
in the air which could hardly be formed
from even large groups of small ions, for
reasons to be mentioned later.

The larger ions of the air and the intermediate
ones are closely related and are the
ones which so far are puzzling the scientists.

Aitken, whose work along this line
is justly famous, believes that the larger
ions of the air are not aggregations of
smaller ions, because when the smaller ions
are formed by radium in a dust-free gas,
the larger ions never appear. For this reason
he believes the larger ions are really
dust particles which have caught a charge
of electricity. The word dust, however,
is a convenient word to cover up our ignorance
of just what the large ions actually
are. In fact, they exhibit some properties
which make them very interesting, and
which show that they are far from being
simple particles of dust.

WHAT ARE ATMOSPHERIC "DUST" PARTICLES?

These dust particles, if they are such,
must not be confused with ordinary wind
dust particles such as those blown up from
a street. They are much finer and smaller,
so much so in fact that they are capable of
remaining suspended in the air for a very
long time. Such particles are too small to
be detected by ordinary means of observation
and they can best be observed and
counted by the famous cloud method. This
method is to take a sample of the air and
put it under reduced pressure which allows
it to expand until the moisture in the air
begins to collect around the dust nuclei,
making them visible. In determining the
relative size of the original particles another
method must be used, and that is to
compare their mobilities. The mobility of
an ion is its rate of motion in an electric
field of one volt per centimeter, and is a
measure of its mass. The larger the mass
the slower the particle will move under the
given force.

By this method the larger ions are found
to be over a thousand times larger than the
small ions and the intermediate ions about
half way between. It is argued that if
these were dust particles only, then all sizes
would be found instead of three distinct
types. Recent discoveries tend to show
there is something more than dust and
electricity in the large ions and that it is
this something else which causes the formation
of the large ions which are not
found anywhere else. It is all due to the
discovery, a few years ago, that water
vapor may condense in two ways on a
rigid surface under certain conditions.

Either it may condense in the ordinary way
as a pure liquid, or it may condense more
slowly and form a very dense atmosphere
of separate water molecules about half way
between a gas and a liquid, which will suddenly
change to a liquid with an increase
of the vapor pressure.

Now the significant thing is that if the
mobilities of the ions are measured carefully
while the pressure of the water vapor
in the gas is being increased, a point is
reached where the intermediate ions suddenly
begin to move slowly like the large
ions as shown in Fig. I, and this has suggested
to J. A. Pollock and others the
following explanation:

The larger ions and
the intermediate ones are formed of minute,
rigid dust-like particles about which
a small amount of water vapor has already
started to condense. About some of these
particles the water vapor has condensed as
a liquid, forming the large ions, while
about others it has only condensed as a
dense atmosphere, forming the intermediate
ions. When the vapor pressure in the
air increases, the dense atmosphere on the
intermediate ions may change to a liquid,
as in Fig. II, and thus the intermediate
ions become large ions in a fraction of
time. This theory is not at all conclusive
but it fits in with the observed facts better
than any other, and is the only one
which explains how the intermediate ions
may suddenly become larger and more
slowly moving. As water vapor only condenses
in this peculiar way on rigid surfaces
under certain conditions, we must
assume that the centers of the intermediate
and larger ions are different from the
smaller ones usually found in gases and
that they contain some small, rigid dust-like
particle. This would also explain why
they are not found in dust-free gases even
tho the small ions are present, and why
they are commonly found in the air.

HOW ATMOSPHERIC PARTICLES ARE ELECTRIFIED

How these particles become electrified is
another and vital question. There are many
possible ways in which the phenomena may
be accounted for. The ultra-violet light
from the sun is a very powerful ionizing
agent, having the power to detach electrons
from the molecules of the air, as it passes
thru the air. This ultra-violet light is particularly
strong in the upper and thinner
layers of the atmosphere, and tho the air
absorbs a great many of these waves on
account of their shortness, still a large
number reach the lower levels of the air.

Some more visionary theorists claim that
ions and electrified particles are actually
carried in huge streams from the sun to
the earth, and there is some striking evidence
that this may be true during periods
of the sun's greatest activity. Friction is
a great producer of electric charges, as is
evidenced by the action of the well known
friction static machine, and it is highly
probable that friction of the air and dust
particles in the air may be one of the potent
causes of the electrification of the air.

Again it may be due in part to radio-active
substances in the earth's surface which constantly
give off electrified particles into the
air.

The mystery of the electricity in the air
is a double one and if we could discover
just how the ions are produced we could
more easily ascertain just what they consist
of. When these two questions are
solved we may be in a position to harness
the "electricity of the air" to our own use.